| Artocarpus heterophyllus is an evergreen tree of Moraceae and Artocarpus.Its calyx,seeds,leaves,bark,wood and sawdust have good edible value,medicinal value and material value.Therefore,it is deeply loved by people.In recent years,studies have found that the albinism of jackfruit will affect its growth and yield to a certain extent.Exploring the traits and molecular mechanism of jackfruit albino seedlings will help to further study the mechanism of jackfruit albino and discover and clone related genes.In this study,the albino mutant of jackfruit was used as the experimental material to determine the content of the intermediate product of its chlorophyll synthesis and metabolism pathway,observe its internal cell structure and chloroplast development and differentiation,and analyze and compare its transcriptome sequencing results for further study of jackfruit mutant The chlorophyll synthesis and metabolism process,chloroplast development mechanism and albino mechanism provide theoretical basis.The main research results are as follows:1.Morphological characteristics of jackfruit normal seedlings and albino seedlingsObservation found that the growth of jackfruit albino seedlings is weaker than that of normal seedlings,and the size of the leaves(normal green leaves are 8-13 cm long and 5-8cm wide;albino leaves are 3-7 cm long and 1.5-4 cm wide)and plant height(Normal green leaves are about 45 cm,albino leaves are about 36 cm)and other traits are also significantly lower than normal seedlings.Using optical microscope and transmission electron microscope to observe the leaf structure and chloroplast ultrastructure of jackfruit,it was found that the mesophyll cells of the albino seedlings were white,and there was no obvious green granular structure in the cells,and there were obvious defects in the development of chloroplasts,and the development of basal particles was impaired..That is,the chloroplast structure in the leaves of jackfruit albino seedlings is abnormal and cannot synthesize chlorophyll normally,which makes the leaves of albino seedlings appear white.2.Physiological and biochemical characteristics of jackfruit normal leaves and albino leaves(1)When measuring the content of chlorophyll precursor substances in leaves,it was found that the synthetic content of substances from δ-aminolevulinic acid(ALA)to protochlorophyll(Pchl)did not show a significant difference,but the final synthesized chlorophyll a and chlorophyll b The carotenoid content is significantly lower than that of normal green leaves,and the content is less than 50% of normal green leaves.It shows that the chlorophyll synthesis of albino seedlings has obstacles between Pchlide→Chlide→Chl a→Chl b.(2)The total soluble sugar and total soluble protein in jackfruit leaves were measured,and it was found that the content of total soluble sugar(76.48 mg/g)and total soluble protein(107.58 mg/g)of albino seedlings was slightly higher than that of normal seedlings(total soluble sugar was 74.89 mg/g;total soluble protein is 106.99 mg/g),there is no significant difference between the two.It shows that there is no obstacle in the synthesis process of soluble total sugar and soluble total protein of albino seedlings,that is,jackfruit albinism has no effect on the material synthesis process of soluble total sugar and soluble total protein.(3)The activity of 5-aminolevulinic acid dehydratase,uroporphyrinogen III synthase,and chlorophyllase were measured,and compared with the results of chlorophyll precursor substances and chlorophyll content determination.The results showed that the chlorophyll before the original chlorophyll was The synthesis process proceeded normally,but the subsequent chlorophyll synthesis process was hindered,resulting in a decrease in the chlorophyll content.3.Transcriptome sequencing analysis of jackfruit normal leaf and albino leafTranscriptome sequencing of jackfruit normal leaves and albino leaves showed that most of the genes related to photosynthesis(photosystem I,photosystem II,and photosynthetic antenna protein synthesis-related genes)in jackfruit albino seedlings showed a downward-regulation trend.It shows that the albino of jackfruit has a negative effect on the development and differentiation of chloroplast and chlorophyll synthesis. |
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